Climate change and soil: sink or source?

Peatlands, or bogs, are wetlands where partially decomposed vegetation accumulates saturated in water. The soil is very rich and productive and contains huge amounts of carbon (flickr).

Julia Poska| November 29, 2018

The world’s soils hold massive amounts of carbon from decomposed plants and animals. In this way the soil acts as a sink, storing carbon that could otherwise end up in the atmosphere, but soil is a source of carbon emissions.

Two studies published this month highlight just how helpful and harmful the the soil’s carbon storage capacity might be in the face of climate change.

The first, published in Proceedings of the National Academy of Sciences, examined the changing role of peatlands, also known as bogs or mires, in the carbon cycle. According to author Qianlai Zhuang of Purdue University, peatlands cover about 3 percent of the Earth’s surface but contain 30 percent of soil carbon. This major sink, though, has begun to release large amounts of carbon, too.

When peatlands are drained for human uses like agriculture or mining, they release some of that carbon into the air. The rate of carbon loss is predicted to increase with climate change, even for untouched peatlands.

Northern-hemisphere peatlands in Canada, Siberia and Southeast Asia have already begun releasing significant amounts of carbon, but Zhuang and PhD candidate Sirui Wang found that Amazonian peatlands may soon follow suit, according to a Purdue University media release. The researchers estimate that by the end of the century, peatlands in that area could release an amount of carbon equal to 5 percent of current annual emissions worldwide.

The second study, published in Nature Climate Change, found increased capacity for carbon storage deep within the soil. Much of the soils carbon is stored in a dissolved form; the carbon leaches downwards in the water and attaches to minerals over 6-feet underground.

Little is known about this method of storage, but Washington State University researcher Marc Kramer and Oliver Chadwick from the University of California Santa Barbara have looked at it closely and believe humanity could take advantage of the process to bury more atmospheric carbon deep inside the earth. Unfortunately, they believe climate change will limit this capacity in tropical rainforests, currently the best locations for dissolved carbon storage.

One thought on “Climate change and soil: sink or source?”

I have worked on the paleoecology preserved in peatlands that shows their long, important history. They are magical places, and it is heartbreaking to watch how humans are destroying them and using the areas for farming, mining, etc.